1. Field of the Invention
The present invention relates to a drive system including an electric machine and a coupling device, the electric machine having stator arrangement and a rotor arrangement and the coupling device having an inlet region, wherein the rotor arrangement and the inlet region are connectable to a drive shaft for joint rotation about an axis of rotation.
2. Description of the Related Art
In drive systems having an electric machine with a rotor arrangement connected to a drive shaft, the electric machine typically comprises a starter/generator arrangement. In an active state, the electric motor acts as a starter arrangement to generate a torque which is transmitted to the drive shaft to start an internal combustion engine. In this active state, the electric machine may also be used to supplement the torque provided by the internal combustion engine by delivering a backup torque or a drive torque. In another state, the electric machine may also be used as a generator for generating electric power and/or actively damping vibrations when the driveshaft is driven by another drive machine such as the internal combustion engine. Because of the limited space available in motor vehicles, a goal of such drive arrangements is to achieve as small an overall size as possible in conjunction with the greatest possible power capability. The general result of this is that the various known drive system assemblies are designed with the smallest possible overall axial length. However, electric machines having larger power capabilities are desired.
An object of the present invention is to provide a drive system having a very small overall axial size that is also easy to mount.
According to the present invention, the object is achieved by a drive system having an electric machine with a rotor arrangement connectable to a drive shaft for joint rotation therewith and a stator arrangement. The drive system further includes a coupling device such as, for example, a hydrodynamic coupling device with an inlet region that is also connectable to the drive shaft for joint rotation therewith. To effect the connection between the coupling device and the drive shaft, the drive system includes a coupling element connectable to the drive shaft and is connected to a rotor interaction region of the rotor arrangement. The coupling element is also connectable to the inlet region of the coupling device for joint rotation therewith.
Accordingly, the coupling element of the drive system according to the present invention which supports the rotor interaction region of the rotor arrangement simultaneously couples the coupling device and the drive shaft. Accordingly, separate coupling assemblies for the rotor interaction region and the coupling device are not required and the coupling device may be arranged axially closer to the electric machine.
The rotary connection between the coupling element and the coupling device may be produced by providing a first engagement formation on the coupling element and a second engagement formation at the inlet region of the coupling device. The first engagement formation and the second engagement formation are axially moveable toward one another to produce a mutual circumferential driving engagement.
One engagement formation of the first and second engagement formations has a plurality of engagement projections which axially engage between two mating driving projections or in a mating driving recess of the other engagement formation of the first and second engagement formations for producing the circumferential driving engagement.
The first and second engagement formations may be designed as Hirth toothings, i.e., serrated toothing. A self-centering effect is obtained by engagement of the Hirth toothings. To retain the engagement of the first and second engagement formations, an engagement holding arrangement is arranged for holding the circumferential driving engagement state of the first and second engagement formations.
The engagement holding arrangement may, for example, include a holding element arranged on one of the coupling element and the rotor interaction region so that the holding element is rotatable relative to the one of the coupling element and the rotor interaction region and supported in the axial direction. The holding element has a third engagement formation. A fourth engagement formation is arranged on the other of the coupling element and the rotor interaction region. The holding element is rotatable relative to the one of the coupling element and the rotor interaction region for bringing the third engagement formation into a holding engagement with the fourth engagement formation.
In one embodiment, the holding element has an essentially sleeve-like engagement section on which the third engagement formation is arranged. The holding element further includes a support section which extends essentially radially and can be supported axially relative to the one of the coupling element and the rotor interaction region. The third and the fourth engagement formations may be arranged for producing a threaded engagement state. The threaded engagement state does not require that the holding element be situated at a specific rotary position to obtain a defined axial coupling.
However, the third and the fourth engagement formations may alternatively be arranged to produce a bayonet lock engagement state.
A tool attachment may be arranged on the holding element for facilitating the rotation of the holding element for bringing the third and fourth engagement formations into the holding engagement to produce an axial retention. The holding element may be locked against rotation with reference to one of the coupling element and rotor interaction region to prevent the undesired release of the holding engagement even during vibrations occurring during operation.
To further reinforce the axial cohesion between the coupling element and the coupling device, i.e., to prestress the coupling element and the coupling device relative to one another, at least a portion of the holding element may be elastically deformed.
The coupling element may be formed as a circular plate. In this embodiment, the first engagement formation is formed by engagement projections which project axially from the coupling element. The engagement projections are preferably formed by reforming.
To compensate and/or absorb wobbling movements which may occur in the region of the coupling device during operation, the coupling element may be formed from a flexible material such as, for example, sheet stock.
The present invention also relates to a mounting device for mounting an electric machine for a drive system, the electric machine having a rotor arrangement which is to be connected to a drive shaft for joint rotation, and a stator arrangement which is to be connected to a fixed assembly.
Electric machines such as synchronous machines with permanent magnets are assembled with only a small air gap between the interaction region of the rotor arrangement and the interaction region of the stator arrangement for increasing the efficiency of the electric machine. The permanent magnets arranged, for example, on the rotor arrangement, exert an attractive force on the stator arrangement. Accordingly, there is a risk that the stator arrangement will be attracted onto the rotor arrangement and adhere to the latter during assembly. Damage to one of the assemblies may occur while the assemblies are detached.
For this reason, the invention provides a mounting device for use during a mounting operation in which the undesired adhering to one another of, or mutual contact between the rotor arrangement and stator arrangement, can be reliably prevented. For this purpose, the mounting device comprises a first guide arrangement which is arrangeable in a fixed fashion relative to the stator arrangement, a second guide arrangement provided on the rotor arrangement. The second guide arrangement interacts with the first guiding arrangement when the rotor arrangement is brought up axially toward the stator arrangement such that the rotor arrangement is guided relative to the stator arrangement when the rotor arrangement is displaced into its assembled position. Once the assembles position has been achieved, the interaction between the first guide arrangement and the second guide arrangement is releasable and the second guide arrangement may be removed from the rotor arrangement.
The second guide arrangement may comprise a plurality of guide pins which are releasably provided on the rotor arrangement and extending essentially in one guiding direction. In this embodiment, the first guide arrangement has a guide opening corresponding to each guide pin in which a respective guide pin engages to-guide the rotor arrangement relative to the stator arrangement in the guiding direction.
To carry out the mounting operation as easily as possible, the guide pins may be borne on a guide pin carrier. This ensures that individual guide pins are not left inadvertently in the system which could lead to damage in an overall drive train in which the system is mounted.
The guide pin carrier includes a mounting prevention arrangement to prevent further assemblies from being connected to the rotor arrangement and stator arrangement before any aids used to facilitate the mounting which are not intended to remain in the system have been removed. The mounting prevention arrangement prevents the subsequent coupling of the rotor arrangement to a further assembly, preferably a coupling device, when the second guide arrangement is not removed after the rotor arrangement and stator arrangement have been joined.
A coupling element of the rotor arrangement may include a feedthrough opening for each guide pin through which a respective guide pin may be guided for the purpose of releasably assembling the rotor arrangement with the second guide arrangement.
The present invention further relates to an electric machine for a drive system comprising a rotor arrangement arranged for being coupled to a drive shaft for joint rotation therewith and a stator arrangement arranged for being coupled to an essentially fixed assembly. The stator arrangement has a stator support having at least one stator support part formed from sheet stock and is connectable to the fixed assembly. The stator arrangement further includes a stator interaction region arranged on the stator support.
The stator support of the electric machine is very easy to produce which lowers the overall costs for such a machine.
In a further embodiment, the stator support comprises a first support part and a second support part, of which at least one is formed from sheet stock. The first support part and the second support part are connected in a first radial inner region to one another and to the essentially fixed assembly. The first and second support parts are connected in a second radially outer region to one another and to the stator interaction region.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.